Hi @maddisonsunshine12
Thank you for contacting us about Photo Gallery Mosaic type question.
As so you are using Mosaic type, on the Main settings Tab it has Image Count Text – you can adjust the background and transparency of your 5th image – http://prntscr.com/hiulpo here – http://prntscr.com/hiukky
Also you can find more details about this type of the gallery here – https://stagging.supsystic.com/documentation/gallery-mosaic-type/
If I understand you wrong, please clarify the expression “so when hovering the photo does not mirror” more detailed.